157981 has 4 divisors (see below), whose sum is σ = 167292. Its totient is φ = 148672.

The previous prime is 157951. The next prime is 157991. The reversal of 157981 is 189751.

157981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 189751 = 31 ⋅6121.

It can be written as a sum of positive squares in 2 ways, for example, as 62500 + 95481 = 250^2 + 309^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-157981 is a prime.

It is a super-2 number, since 2×157981² = 49915992722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a nialpdrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (157901) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4630 + ... + 4663.

It is an arithmetic number, because the mean of its divisors is an integer number (41823).

2¹⁵⁷⁹⁸¹ is an apocalyptic number.

It is an amenable number.

157981 is a deficient number, since it is larger than the sum of its proper divisors (9311).

157981 is an equidigital number, since it uses as much as digits as its factorization.

157981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9310.

The product of its digits is 2520, while the sum is 31.

The square root of 157981 is about 397.4682377247. The cubic root of 157981 is about 54.0590346604.

The spelling of 157981 in words is "one hundred fifty-seven thousand, nine hundred eighty-one".